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Polyoxometalates-Graphene oxide Hybrids : Synthesis, Structure and Electrochemical applications

Title
Polyoxometalates-Graphene oxide Hybrids : Synthesis, Structure and Electrochemical applications
Translated Title
폴리옥소메탈레이트 – 그라핀옥사이드 하이브리드의 합성, 구조 및 전기화학 분야의 적용
Authors
Kim, Yong
DGIST Authors
Kim, Yong; Shanmugam, Sangaraju
Advisor(s)
Shanmugam, Sangaraju
Co-Advisor(s)
Choi, Young Woo
Issue Date
2014
Available Date
2016-05-18
Degree Date
2014. 2
Type
Thesis
Keywords
polyoxometalateKeggin typeheterogeneous catalystelectrochemical activitycomposite membrane전기화학 특성복합전해질막
Abstract
The deposition of POM on chemically reduced graphene oxide sheets was carried out through electron transfer interaction and electrostatic interaction between POM and graphene sheets to make heterogeneous catalyst in aqueous media. Well dispersed individual PMo clusters were observed by the electron microscopy and atomic force microscopy measurements. The interaction between polyoxometalate and the graphene oxide sheet was confirmed by using various spectroscopic methods such as FT-IR, UV-VIS, and Raman. The UV-Visible, IR and cyclic voltammetry results revealed the alteration of electronic structure of deposit-ed PMo as a result of strong interaction with the graphene surface. Electrochemical properties of PMo-rGO catalyst was investigated in an aqueous acidic electrolyte. The hybrid catalyst showed enhanced electro-oxidation of nitrite compared with pure homogeneous PMo and rGO. Further, POMs were investigated for high proton conductive membranes composited with Nafion for polymer electrolyte membrane fuel cell (PEMFC) under low relative humidity. (The investment of POMs is performed to contain lots of water molecules through hydrogen bond.) POMs were immobilized by modified graphene oxide to prevent it from leaching out during operation. A Nafion/PW-mGO composite membrane provided high amount of bound water so that the proton conductivity was shown higher than Nafion 212 membrane. Fuel cell performance of Nafion/PW-mGO composite membrane exhibited the higher power density of 841 mW cm -2, operating at a temperature of 80 °C under 18% RH in contrast with Nafion 212 and recast Nafion, operating under identical conditions, a peak power density of 210 mW cm-2 and 208 mW mW mW cm -2 were observed. The composite membrane could be a potential membrane for fuel cell operating under low relative humidity. ⓒ 2014 DGIST
Table Of Contents
Ⅰ. INTRODUCTION 1 -- 1.1 Foreword 1 -- 1.2 Objective of the study 2 -- 1.2.1 Polyoxometalates-reduced graphene oxide immobilized hybrid catalyst 2 -- 1.2.2 Efficient proton conducting Nafion / polyoxometalates - modified graphene oxide membrane 2 -- 1.3 Theoretical Background 7 -- 1.3.1 Structure of Keggin type polyoxometalate 7 -- 1.3.2 Electrochemical activities of Keggin type polyoxometalate 10 -- 1.3.3 Support material of polyoxometalate for heterogeneous catalyst 13 -- 1.3.4 Properties, and structure of graphene support material 15 -- 1.3.5 Electrochemical application of polyoxometalates 18 -- 1.3.6 Nitrite oxidation reaction 18 -- 1.3.7 Proton exchange membrane 19 -- 1.3.8 Polyoxometalate composite membranes 23 -- Ⅱ. EXPERIMENTAL SECTION 25 -- 2.1 Polyoxometalates – reduced graphene oxide hybrid catalyst 25 -- 2.1.1 Preparation of graphene oxide 25 -- 2.1.2 Preparation of reduced graphene oxide 25 -- 2.1.3 Preparation of PMo-rGO catalysts 26 -- 2.1.4 Characterization 26 -- 2.2 Nafion / Polyoxometalate–modified graphene oxide composite membrane 28 -- 2.2.1 Preparation of modified graphene oxide 28 -- 2.2.2 Preparation of PW-mGO hybrid material 28 -- 2.2.3 Fabrication of Nafion / PW-mGO composite membrane 28 -- 2.2.4 PW-mGO Characterization 29 -- 2.2.5 Membrane characterization 29 -- 2.2.6 Fabrication of membrane electrode assembly and fuel cell performance evaluation 31 -- Ⅲ. RESULTS 30 -- 3.1 Phosphomolybdic acid – reduced graphene oxide hybrid catalyst 33 -- 3.1.1 Morphology analysis 33 -- 3.1.2 Characterization of PMo-rGO 36 -- 3.1.3 Electrochemical activities 42 -- 3.1.4 Electrochemical oxidation of nitrite ion 46 -- 3.2 Nafion /Phosphomolybdic aicd–modified graphene oxide composite membrane 51 -- 3.2.1 Characterization of PW-mGO 51 -- 3.2.2 Membrane characterization 56 -- 3.2.3 Fabrication of membrane electrode assembly and fuel cell performance evaluation 59 -- IV. CONCLUSIONS 62 -- V. REFERENCES 63
URI
http://dgist.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002262539
http://hdl.handle.net/20.500.11750/1347
DOI
10.22677/thesis.2262539
Degree
Master
Department
Energy Systems Engineering
University
DGIST
Files:
Collection:
Energy Science and EngineeringThesesMaster


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